The present invention relates to a method of in situ reactive gas plasma treatment, and more particularly to a method for removing a residue remained inside a metal etching chamber and/or on a wafer after completing a metal etching process.
In the process for manufacturing an integrated circuit, a plasma etching process is often used to remove the metal, such as aluminum, remained on the surface of a wafer during the metallization process of forming connecting lines. An etching gas is introduced to a metal etching chamber, followed by applying an electromagnetic power to the metal etching chamber for producing plasma derived from the etching gas to react with a portion of aluminum metal uncovered by the photoresist. The formed products are then removed out of the metal etching chamber by vacuum pumps.
Immediately after finishing the metal etching process, there are some residues remained in the metal etching chamber, that is, byproducts of the reaction between the plasma and the metal part uncovered by the photoresist can not be immediately removed out of the metal etching chamber by vacuum pumps. The residues remained on the wafer and/or in the metal etching chamber are white powders containing metal, photoresist, and components of the plasma. Particularly, the grain or powder with a large particle size can be observed by a microscope or even naked eyes. This kind of residue can not be removed after the plasma etching process even though all vacuum pumps are opened. Thus, it is necessary to interrupt the metal etching process and open the metal etching chamber to manually clean and remove the residues at a certain period of time when the amount and the particle size of the residues exceed a certain tolerance. It will decrease the production efficiency because of interrupting the metal etching process too often. Furthermore, the residues with large particle size remained on a wafer will influence the quality of the wafer.
The plasma etching method has been widely used in manufacturing process of integrated circuits and chemical industry. U.S. Pat. No. 4,816,113 discloses a method of using oxygen or a compound thereof as a gas source of chemical vapor deposition (CVD) and removing undesired residues from the reaction chamber by plasma etching after deposition of a carbon film on a substrate. However, it is not suitable for removing the residues produced after the metal etching procedure. Furthermore, before introducing oxygen and/or a compound thereof into a reaction chamber, the wafer with a coated film has to be removed from the reaction chamber, but it can not contribute anything to the particle performance of the metal etching chamber.
In addition, U.S. Pat. No. 4,992,137 discloses another method to prevent the formation of etching residues at low temperature, wherein the wafer is kept at low temperature, and the state of plasma in the reaction chamber is maintained to prevent the byproduct of reaction from being deposited on the wafer, and then an inert gas is introduced to eliminate the byproduct in a form of plasma. However, this method can not be applied to remove the residues formed in the metal etching process.
Therefore, it is tried by the applicant to deal with the situation encountered by the prior art.
The object of the present invention is to provide a novel method for removing the residue remained inside a metal etching chamber and/or on a wafer after completing a metal etching process.
It is another object of the present invention to provide a method of in situ reactive gas plasma treatment to improve the particle performance of a metal etching chamber.
According to the present invention, the method includes the steps of (a) vacuating the metal etching chamber after the metal etching process, (b) introducing a reactive gas to the metal etching chamber, (c) applying an electromagnetic power to the metal etching chamber for producing a plasma derived from the reactive gas to remove the residue inside the metal etching chamber and/or on the wafer.
In accordance with one aspect of the present invention, the metal etching process is a plasma etching process for forming a metal connecting line on the wafer.
In accordance with another aspect of the present invention, the residue is a white powder including metal, photoresist, and components of an etching gas.
Preferably, the metal is an aluminum alloy.
Preferably, the etching gas includes BCl3, Cl2, and N2 or Ar.
Preferably, the reactive gas is BCl3.
Preferably, the flow rate of the reactive gas is about 100 sccm.
Preferably, the method is executed before removing the wafer out of the metal etching chamber.
Preferably, the electromagnetic power is a radio frequency power (r.f. power).
Preferably, the plasma reacts with the residue for 10 seconds.
In accordance with another aspect of the present invention, after the step of (c), the method further includes a step of (d) vacuating the metal etching chamber.
Another object of the present invention is to provide a method for removing a residue remaining in a plasma etching chamber and on a wafer after a plasma etching process. The method includes the steps of (a) introducing a reactive gas to the plasma etching chamber, and (b) applying an electromagnetic power to the plasma etching chamber for producing a plasma derived from the reactive gas to remove the residue inside the plasma etching chamber and on the wafer.
In accordance with one aspect of the present invention, before the step (a), the method further includes a step of vacuating the plasma etching chamber after completing the plasma etching process.
In accordance with another aspect of the present invention, the plasma reacts with the residue to form a gaseous mixture.
In accordance with another aspect of the present invention, the gaseous mixture is removed by vacuating the plasma etching chamber.
Preferably, the plasma etching process is a metal etching process for forming a metal connecting line on the wafer.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: